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Multi-User Communication Channels: Capacity, Duality, and Cooperation

by

Nihar JindalDepartment of Electrical Engineering
Stanford University

Monday, February 23, 20042:15 pm

402 Walter Library

Download slides (pdf 1.82 MB)Over the last decade, wireless communication has transformed from a niche technology into a vital component of most people's lives. The resultant desire to increase capabilities of wireless systems and to use wireless communication in new applications such as distributed sensing brings many technical challenges. In this talk we will discuss the channel capacity, which is defined as the set of all simultaneously achievable data rates, of multi-user communication systems. In the first part of the talk, we will establish a duality between the uplink and downlink channels. This duality allows us to characterize the uplink capacity in terms of the downlink capacity, and vice versa. We will then discuss multiple-antenna versions of the uplink and downlink channels, and see how duality applies to these channels. In addition, we will show how duality can be used to establish capacity results for multiple-antenna channels.

In the final part of the talk, we will consider the value of cooperative communication in ad-hoc/sensor networks. We consider a scenario where two transmitters wish to communicate with two receivers. By allowing the two transmitters to cooperate, and/or allowing the two receivers to cooperate, we can significantly increase the capacity of the system. However, this cooperation comes at some cost. We impose a system-wide power constraint to incorporate the cost of cooperation and evaluate the improvement offered by different modes of cooperation.

Nihar Jindal received the B.S. degree in Electrical Engineering and Computer Science from U.C. Berkeley in 1999 and the M.S. degree in Electrical Engineering from Stanford University in 2001. He is currently completing his PhD in electrical engineering at Stanford University, and expects to receive his degree in the summer of 2004. At Stanford, he works with Prof. Andrea Goldsmith in the areas of communication and information theory.